1. Field of the Invention
The invention relates to a memory chip, and more particularly to a memory device which can detect the occurrence of a die boundary crossing operation between two memory chips by monitoring a wait pad.
2. Description of the Related Art
For a conventional memory chip, such as a CRAM (cellular RAM) chip, after the last word on an active word line is read/written, a boundary crossing operation is performed to switch the reading/writing operation to a next word line; that is, the one word line becomes inactive while the next word line becomes active. The reading/writing operation can be performed continuously on the next word line. When the boundary crossing operation is performed, a signal at a wait pad of the memory chip is asserted until the next word line is active. Thus, by monitoring the wait pad, status of the reading/writing operation may be known by users.
In some applications, at least two memory chips can be stacked to form a memory device. A boundary crossing operation may be performed between the last word line of a top memory chip and the first word line of a bottom memory chip; that is, the last word line of the top memory chip becomes inactive while the first word line of the bottom memory chip becomes active. In this case, the boundary crossing operation is referred to as a “die boundary crossing operation”.
Thus, it is desired to provide a memory device which can detect the occurrence of a die boundary crossing operation between two memory chips.